Eccentric rotor sliding vane compressors generally separate the entrained oil from the air in two stages. The primary stage may consist of a tortuous passage or an impingement shield situated adjacent the outlets from the rotor stator unit, and a proportion of the oil droplets are induced to coalesce on the surface of the passage or the impingement shield and are then returned to the sump. The secondary separation stage may consist of one or more felt pads or other filtering or coalescing media adapted to remove the majority of the remaining oil from the compressed air. It is desirable that the separation of the oil from the compressed air be as efficient as possible, firstly because it is frequently inconvenient for the compressed air to have a significant amount of entrained oil in it, and secondly because oil that is not separated is lost and must subsequently be replaced.